The invention relates to a stator for an eccentric screw pump or an eccentric worm motor, and includes an outer tube that is provided with a lining of rubber or a rubber-like material and has a hollow space or cavity, in the shape of a double or multiple spiral, for accommodating a rigid rotor that is also in the form of a spiral, whereby the stator respectively has one spiral more than does the rotor.
The manner of operation of eccentric screw pumps and eccentric worm motors is also designated as the Moineau principle. From DE 44 03 598 A1 a stator of the aforementioned type is known according to which the lining is fixedly connected with the outer tube, i.e. via chemical bonding between the elastomeric lining and a metallic outer tube. The outer tube of this stator has a cylindrical shape. However, stators are also known according to which the shape of the outer tube is adapted to the shape of the hollow space or cavity surrounded by the lining such that the thickness of the lining, in other words the spacing between the hollow space and the outer tube, is continuously the same or nearly the same. With both embodiments of the previously known stators there exists the danger that the fixed connection between lining and outer tube becomes detached, primarily if during the operation the stator is subjected to high temperatures and/or chemical stresses. Even if the lining can withstand these stresses, a detachment from the outer tube occurs if a bonding agent is used that cannot withstand either the thermal and/or the chemical conditions.
There are rubber types, such as HNBR fluoro rubbers or silicone rubbers, which at temperatures of 160° C. and greater remain functional, yet even with these rubbers the rubber/metal connection can become problematic and can be destroyed during continuous use.
It is an object of the invention to provide a stator that remains functional even under those conditions where the fixed connection between the lining and the outer tube could be destroyed, e.g. by chemical influences or high temperatures.